nhodges,I refilled it with approx. 25ml of 10000cst from toyota.

pberku,the fluid leaks out from the seal on the pin hole and you can tell by looking at your fan to see if there is any greasy dirt on the blades(like mine).

psfred,you have been very helpful in this matter (thanx).The howl is there at any temp and is really noticeable between 2500 and 4000rpm.
Is that the way it's supposed to be?Just sounds too loud for a benz.